This inventin relates to a method of installing a hollow, curved steel pipe in the ground by forcibly introducing a curved steel pipe, and especially a curved steel pipe of relatively small diameter, into the ground at a prescribed angle either from the surface of the ground, or from inside a shaft or tunnel, while excavating and conveying away the earth and sand accumulating inside said pipe with an auger; as well as to a machine that is useful for practicing this method.
The forcible introduction of a straight steel pipe has been frequently practiced in the past, but that of forcibly introducing a curved steel pipe into the ground has not been known. The following methods have been employed in the case of forcibly introducing a straight steel pipe: (1) that of mounting a small shield at the distal end of the straight steep pipe and jacking the steel pipe from its rear end while excavating the earth and sand with the small shield; (2) that of fitting a water-jetting device at the distal part of the straight steep pipe and breaking down and excavating the facing with this jetting device while jacking the straight steel pipe from its rear end; or (3) that of forcibly introducing the straight steel pipe by jacking alone without excavating the facing.
However, in the case of method (1), above, it is not possible to use a shielding machine of a diameter less than 1.5 meters because of mechanical and operational restrictions. Hence, this method cannot be operated in the case of pipes of small diameter. Further, in view of the functions of a shielding machine, this method can scarcely be applied in the case of curved steel pipes whose radius of curvature is less than 50 meters. In the case of method (2), above, the water jet disturbs the ground around the steel pipes, and since the excavation is carried out to excess, difficulty is experienced in introducing the pipe with accuracy by the employment of this method. In addition, this method is objectionable from the standpoint of land subsidence and safety. Furthermore, labor is needed in handling the mud that results from the water jet. On the other hand, in the case of method (3), above, difficulty is experienced in introducing the pipe when the ground condition is hard, with the consequence that when the introduction is forced, the accuracy of the introduction becomes poor. Hence, when this method is applied to a curved steel pipe, it will become still more difficult to expect favorable results.